COMMUNISTS ARE HOPING TO PICK FRUITS OF MITTERRAND'S TRIUMPH

By RICHARD EDER, Special to the New York Times

Published: June 12, 1981

CREIL, France, June 11—
All around this Picardy town, the posters are up for the rival candidates in Sunday's first-round legislative elections. Maurice Bambier's display an affable, corpulent man under a big headline that reads: ''Candidate of the United Left Majority.'' In the bottom right-hand corner, and in very small type, there is the additional notation: ''Presented by the Communist Party.''

It is unexampled modesty in a party that has always blown its horn as loudly as possible. Severely damaged by the victory of the Socialist Party in the recent presidential election, the Communists are trying to get across the idea that Francois Mitterrand's triumph was theirs too.

Outside the Usinor steel-laminating plant on the edge of town, three workers unroll a large poster proclaiming that Mr. Mitterrand's election was the first stage in the victory of the French left, and that the second stage requires people to vote for as many Communist deputies as possible.

The unrolling was timed to coincide with the arrival of Jean Anciant, the Socialist candidate, outside the factory gates. Mr. Anciant had come to do some lunch-hour handshaking, and although he exhibited a tolerant smile there were were holes in it. ''They act as though Mitterrand had been their candidate,'' one of his supporters complained. 2 Leading Candidates Picked

Sunday's vote will select the two top-running candidates for the second round. Since the right has produced a mostly united list, a conservative candidate will be one of the finalists in virtually every one of France's 491 election districts. Only a minority of these are expected by political commentators here to win in the second round, given the country's evident

What will be crucial to the manner in which Mr. Mitterrand and his Socialists will run the country over the coming years is whether they can knock out enough Communist candidates on Sunday so that they can command a majority or near-majority in the Assembly after the second round, and thus be freed from depending on Communist support to get their program through.

Thus there is a fretful rivalry between the two parties this week, coming after a long history of bitter division and brief periods of guarded truce. At the same time both parties are trying to put as good a face on things as possible, aware that at least temporary unity of the left is needed to beat the right in the second round. It is like one of those family photographs whose grins promise chairthrowing once the shutter snaps.

The strains are particularly evident in this southern Picardy district, perhaps because it exemplifies so neatly the shifting political currents and precarious balances of these past few months. '1 Percent of France'

''We are 1 percent of France,'' Mr. Anciant said the other day, referring to the Department of the Oise, of which Creil is a principal town. Its 600,000 inhabitants make it a kind of median among the 96 French departments; so does its per capita income. Mr. Anciant's district includes the industrial area around Creil, an agricultural and tourist area around the towns of Chantilly and Senlis to the west, and a population of commuters to Paris, 40 miles south.

Mr. Anciant, 47 years old, is Mayor of Creil, a lifetime Socialist and an unswerving follower of Mr. Mitterrand. He is an economics professor and a worker's son. His father assembled bicycle wheels at home at night to pay for the son's education.

This is the third time he has run for the Assembly. In the previous races he was beaten in the first round by Mr. Bambier, the Communist, although by diminishing margins. Each time, Mr. Bambier went on to lose to the conservative candidate, Arthur Duhaine, who is Mayor of Senlis.

This time Mr. Anciant believes that the surge of Socialist strength throughout the country will put him ahead of Mr. Bambier, and that with the left represented by a Socialist, he can go on to defeat Mr. Duhaine. Both Mr. Duhaine and Mr. Bambier, though insisting that the results are unforeseeable, conceded that Mr. Anciant had a good chance.

Mr. Anciant is a strong believer in his party's program of major economic and social changes. He accepts the party's position that the Communists should be accepted as allies, providing they accept a series of positions - on Afghanistan, on Poland, on internal democracy - that would virtually stand the French Communist Party on its historical head.